1. Field of the Invention
The present invention relates to a presentation system used in a lecture or the like which is performed while indicating a point on an image projected on a screen by a laser pointer, and in particular, relates to a development of a system for using a laser pointer safely.
2. Description of the Related Art
In a case in which a presentation such as a lecture is performed using a liquid crystal projector or the like, a laser pointer for projecting laser beam on a screen to indicate a point for attention thereon is often used. With such a laser pointer, there is a risk that the laser beam will be made incident on the eye of a person in the audience due to an erroneous emission. In Japanese Patent Application Laid-Open (JP-A) 10-4228 publication, as a safety measure for avoiding such a risk, there has been disclosed a technique in which emission of laser beam is automatically turned on/off according to the brightness of an object (a screen or the like) at which the laser beam is directed, and the laser beam is emitted only when the brightness of the object to be projected on exceeds a predetermined threshold value. Also, in JP-A 2000-321530 publication, there has been disclosed a technique in which an angle in a vertical direction or a horizontal direction is detected, and a laser beam is emitted only when the angle is in a predetermined angle range.
In the safety measures disclosed in each of these publications, since a laser beam is emitted if the apparatus disclosed therein should not operate precisely, such a measure cannot be a basic measure. That is, in the technique disclosed in the former publication, a place other than the screen may have a brightness exceeding the threshold value due to an illumination condition, and the laser beam may be projected to that place even when some people in the audience are located therein. Also, in the technique disclosed in the latter publication, since some people of an audience are found within a projection angle of a laser beam due to there being such sites such as a stair seat, a second floor seat, or the like, a laser beam may be directed to the people located in such sites.
Accordingly, an object of the present invention is to provide a presentation system using a laser pointer, which can reliably prevent an erroneous emission of laser beam and can establish sufficient safety.
According to a first aspect of the present invention, there is provided a presentation system comprising a screen, a laser pointer operated by a user to project laser beam on the screen, and an infrared light projector for emitting infrared light on the entire surface of the screen. The laser pointer comprises an infrared light receiving section directed in the same direction as a projection direction of laser beam for receiving infrared light projected from the infrared light projector and reflected from the screen, and a control section for causing the laser pointer to project laser beam only while the infrared light receiving section is receiving infrared light.
According to the first aspect of the invention, when the laser pointer is directed to the screen, the infrared light receiving section provided at the laser pointer receives infrared light reflected from the screen. At this time, laser beam is emitted from the laser pointer and the laser beam is projected onto the screen. On the other hand, when the laser pointer is directed away from the screen, the infrared light receiving section does not receive the infrared light reflected from the screen so that laser beam is not projected. That is, only when the laser pointer is directed toward the screen, a laser beam is projected. Accordingly, erroneous emission of laser beam is prevented beforehand so that a presentation can be performed safely.
Next, according to a second aspect of the invention, there is provided a presentation system comprising: a screen; a laser pointer operated by a user to project laser beam on the screen; an infrared light projector provided in the laser pointer for emitting infrared light in the same direction as an emission direction of laser beam; an infrared light receiving section for receiving infrared light emitted from the infrared light projector and reflected from the screen; and a control section for causing the laser pointer to project laser beam only while the amount of light received by the infrared light receiving section is equal to or greater than a predetermined amount.
According to the second aspect of the invention, when the laser pointer is directed to the screen, infrared light is projected on a screen from the infrared light projector provided in the laser pointer, and the infrared light is reflected by the screen to be received on the infrared light receiving section. In this case, when the amount of light received by the infrared light receiving section becomes equal to or greater than the predetermined amount, laser beam is projected from the laser pointer by the control section, and the laser beam is projected onto the screen. On the other hand, when the laser pointer is directed away from the screen, since the emitted amount of infrared light projected on the screen from the infrared light projector decreases and the reception amount of infrared light received by the infrared light receiving section also decreases to less than the predetermined amount, laser beam is not projected. That is, laser beam is projected only when the laser pointer is directed to the screen. Accordingly, erroneous emission of laser beam is prevented beforehand so that a presentation can be made safely.